Summary
This 1991 paper by Linda B. Buck and Richard Axel reports the discovery of a large multigene family encoding odorant receptors in the rat olfactory epithelium, providing the first molecular basis for odor recognition. The central thesis is that mammals possess a diverse repertoire of G-protein-coupled receptors (GPCRs), each likely tuned to specific odorants, and that combinatorial activation of these receptors allows discrimination of thousands of distinct smells. The authors cloned and sequenced 18 candidate receptor genes, showing they belong to a novel multigene family expressed exclusively in olfactory sensory neurons. A reader takes away that odor perception begins with receptor-ligand binding, that the olfactory system uses a "one neuron, one receptor" rule (later confirmed), and that this work launched the molecular study of olfaction, earning Buck and Axel the 2004 Nobel Prize.
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Key concepts
- Multigene family — A set of genes with similar sequences, arising from duplication, that encode related proteins; here, ~1,000 odorant receptor genes in mammals.
- Odorant receptor (OR) — A GPCR expressed on olfactory cilia that binds volatile odor molecules, initiating a signal transduction cascade.
- Combinatorial coding — The mechanism by which each odorant activates a unique combination of ORs, enabling discrimination of a vast array of scents from a limited receptor set.
- Olfactory epithelium — The nasal tissue containing sensory neurons that express ORs and project to the olfactory bulb.
- G-protein-coupled receptor (GPCR) — A seven-transmembrane-domain protein that activates intracellular signaling via G proteins upon ligand binding.
- One neuron–one receptor rule — The principle that each olfactory neuron expresses only one OR gene, ensuring specificity in odor detection.